- Alkylperoxy and Alkyl Radicals. 5. Infrared Spectra and Ultraviolet Photolysis of t-C4H9O2 Radicals in Argon plus Oxygen Matrices
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tert-Butyl radicals formed by the pyrolysis of azoisobutane were isolated in matrices of Ar + 10percent 16O2 and Ar + 5percent 16O2 + 5percent 18O2.IR spectra of the resulting trapped species were obtained before and after irradiation of the matrices with a medium-pressure Hg arc lamp.In the 1200-200-cm-1 spectral range, nine absorption bands were observed and assigned to the tert-butylperoxy radical.A summary of the known vibration frequencies assigned to primary, secondary, and tertiary alkylperoxy radical centers is presented.
- Chettur, G.,Snelson, A.
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- General Synthesis of Ordered Mesoporous Carbonaceous Hybrid Nanostructures with Molecularly Dispersed Polyoxometallates
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Hybrid nanomaterials with controlled dimensions, intriguing components and ordered structures have attracted significant attention in nanoscience and technology. Herein, we report a facile and green polyoxometallate (POM)-assisted hydrothermal carbonization strategy for synthesis of carbonaceous hybrid nanomaterials with molecularly dispersed POMs and ordered mesopores. By using various polyoxometallates such as ammonium phosphomolybdate, silicotungstic acid, and phosphotungstic acid, our approach can be generalized to synthesize ordered mesoporous hybrid nanostructures with diverse compositions and morphologies (nanosheet-assembled hierarchical architectures, nanospheres, and nanorods). Moreover, the ordered mesoporous nanosheet-assembled hierarchical hybrids with molecularly dispersed POMs exhibit remarkable catalytic activity toward the dehydration of tert-butanol with the high isobutene selectivity (100 %) and long-term catalytic durability (80 h).
- Chen, Chunhong,Fan, Zhanxi,Ge, Yiyao,Ma, Qinglang,Mao, Shanjun,Qi, Guodong,Tan, Chaoliang,Wang, Yong,Wang, Zhe,Xu, Jun,Zhang, Xiao
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- Key Roles of Lewis Acid-Base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion
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The effects of surface acidity on the cascade ethanol-to-isobutene conversion were studied using ZnxZryOz catalysts. The ethanol-to-isobutene reaction was found to be limited by the secondary reaction of the key intermediate, acetone, namely the acetone-to-isobutene reaction. Although the catalysts with coexisting Br?nsted acidity could catalyze the rate-limiting acetone-to-isobutene reaction, the presence of Br?nsted acidity is also detrimental. First, secondary isobutene isomerization is favored, producing a mixture of butene isomers. Second, undesired polymerization and coke formation prevail, leading to rapid catalyst deactivation. Most importantly, both steady-state and kinetic reaction studies as well as FTIR analysis of adsorbed acetone-d6 and D2O unambiguously showed that a highly active and selective nature of balanced Lewis acid-base pairs was masked by the coexisting Br?nsted acidity in the aldolization and self-deoxygenation of acetone to isobutene. As a result, ZnxZryOz catalysts with only Lewis acid-base pairs were discovered, on which nearly a theoretical selectivity to isobutene (～88.9%) was successfully achieved, which has never been reported before. Moreover, the absence of Br?nsted acidity in such ZnxZryOz catalysts also eliminates the side isobutene isomerization and undesired polymerization/coke reactions, resulting in the production of high purity isobutene with significantly improved catalyst stability (2% activity loss after 200 h time-on-stream). This work not only demonstrates a balanced Lewis acid-base pair for the highly active and selective cascade ethanol-to-isobutene reaction but also sheds light on the rational design of selective and robust acid-base catalyst for C-C coupling via aldolization reaction.
- Sun, Junming,Baylon, Rebecca A. L.,Liu, Changjun,Mei, Donghai,Martin, Kevin J.,Venkitasubramanian, Padmesh,Wang, Yong
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- Designing ferrierite-based catalysts with improved properties for skeletal isomerization of n -butene to isobutene
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The crystal morphology and size of ferrierite catalysts were controlled by a suite of crystallization methods and structure-directing agents. In particular, nano-sized ferrierite could be obtained by using tetramethylammonium hydroxide and pyrrolidine as double structure-directing agents under dynamic crystallization. The catalysts were analysed by XRD, SEM, N2 adsorption-desorption, NMR, XRF, NH3-TPD, Py-IR, and TGA, and the characteristics were correlated with their catalytic performance in the skeletal isomerization of n-butene. The results clearly indicated that all the catalysts have a similar crystallinity, Si/Al ratio, and total number of acid sites, while a decrease in their crystal size leads to more pore mouth acid sites. The nano-sized ferrierite showed better stability and higher activity, which were related to their crystal morphology, size, and pore mouth acid. In addition, we further confirmed that high isobutene selectivity can be produced by monomolecular reaction.
- Hu, Haiqiang,Ke, Ming,Zhang, Ka,Liu, Qiang,Yu, Pei,Liu, Yang,Li, Changchun,Liu, Wen
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- A combined experimental and theoretical study of the homogeneous, unimolecular decomposition kinetics of 3-chloropivalic acid in the gas phase
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Decomposition kinetics of 3-chloropivalic acid in the gas phase were determined in a static system over the temperature and pressure ranges of 380.5-430.1 °C and 43-120 Torr, respectively. The reaction, in vessel seasoned with allyl bromide, and in the presence of free-radical suppresser toluene, is homogeneous, unimolecular, and follows a first-order rate law. The rate coefficients are given by the following equation: log k1 (s-1) = (12.42 ± 0.36) - (205.8 ± 4.7) kJ mol-1(2.303RT)-1. The reaction mechanism for the formation of isobutene, hydrogen chloride, and carbon dioxide has been theoretically characterized. The theoretical study, at MP2/6-31G** computational level, points out that the molecular mechanism corresponds to a concerted and highly synchronous process yielding the products. An analysis of bond orders and NBO charges shows that the polarization of the C-Cl breaking bond can be considered the driving force for this fragmentation process. The rate coefficients obtained from experimental data and theoretical calculations are in good agreement.
- Chuchani,Rotinov,Andres,Domingo,Safont
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- Catalytic Behavior of Pt/SbOx for Selective Oxidation of i-C4H10 and i-C4H8 in Stationary and Nonstationary Conditions
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It was found that Pt/SbOx catalysts were active for the selective oxidation of i-C4H10 and i-C4H8 to methacrolein (MAL) at 773 K. The SbOx itself was inactive for the selective oxidation of i-C4H10, while i-C4H8 was converted to MAL on the SbOx. Small amounts of Pt (0.2-0.72 wt%) supported on the SbOx promoted the i-C4H10 oxidation with good selectivity to MAL (typically 50-60%) and MAL+i-C4H8 (80-90%). The selective oxidation of i-C4H8 to MAL was also markedly enhanced by Pt. The performance of Pt/SbOx catalysts for the i-C4H10 selective oxidation may be attributed to combinative catalysis of Pt particles modified with SbOy (y 6O13 produced under the oxidation conditions.
- Inoue, Tomoya,Asakura, Kiyotaka,Iwasawa, Yasuhiro
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- A Fourier-transform Infrared and Catalytic Study of the Evolution of the Surface Acidity of Zirconium Phosphate following Heat Treatment
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The surface acidity of zirconium phosphate at different stages of dehydration and heat treatments has been studied by Fourier-transform infrared spectroscopy of adsorbed pyridine, acetonitrile and acetone and by catalytic cativity in the isomerization of but-1-ene.Broensted-acidic surface POH and P(OH)2 groups are identified -1, respectively> whose strenght increases slightly on bulk dehydration.They are thought to be responsible for the activity in but-1-ene isomerization, which also increases during condensation to pyrophosphate.Lewis-acidic sites of medium-high strenght have also been found, and responsible for the formation of chemisorbed forms of pyridine (ν8a = 1610 cm-1), acetonitrile -1> and acetone -1>.Surface ZrOH groups are also detected on the layered ZrP2O7 surface.The results illustrate the role of exposed planes, both parallel and perpendicular to the layered structure.
- Busca, Guido,Lorenzelli, Vincenzo,Galli, Paola,Ginestra, Aldo La,Patrono, Pasquale
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- Isobutane Dehydrogenation Assisted by CO2 over Silicalite-1-Supported ZnO Catalysts: Influence of Support Crystallite Size
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The ZnO catalysts supported on Silicalite-1 zeolites with different crystallite sizes (0.08, 0.35, 1 and 1.7 μm, respectively) and 5% Zn were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N2 adsorption, SEM, TEM-EDX, DRIFT spectra and NH3-TPD, and their catalytic performance in isobutane dehydrogenation assisted by CO2 was investigated. The catalytic activity is strongly dependent on the crystallite size of Silicalite-1 support. The ZnO/S-1-0.35 catalyst with ca. 0.35 μm crystallite size displays the highest activity, affording an initial isobutane conversion of 51.0% and 74.5% isobutene selectivity. This can be attributed to a higher amount of acid sites present on this catalyst as well as the largest amount of nest silanols possessed by the S-1-0.35 support.
- Luo, Yajun,Wei, Chunling,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
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- Investigations into the origin of the remarkable catalytic performance of aged H-ferrierite for the skeletal isomerization of 1-butene to isobutene
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The catalytic properties of the proton form of six different 10-ring zeolites (clinoptilolite, ferrierite, ZSM-22, SUZ-4, ZSM-57, and ZSM-5), together with the dealuminated analogs of some of these materials prepared via oxalic acid treatment, are compared in the skeletal isomerization of 1-butene. While the pore shape of 10-ring channels in this series of medium-pore zeolites was found to be the key parameter substantially governing the isomerization activity, the catalytic data obtained from two H-ferrierites with similar Si/Al ratios but different crystal sizes reveal that the rate of coke formation on this particular zeolite structure, as well as its isobutene selectivity, can differ significantly according to the zeolite crystal size. The overall results of our study strongly suggest that the remarkable isobutene selectivity of aged H-ferrierite is a consequence of pore mouth shape catalysis over the Bronsted acid sites located near the 10-ring pore mouths with a suitable degree of ellipticity, which may come not only from the unique geometrical constraints imposed by the dual pore system of this particular zeolite, but also from its behavior of being normally synthesized with a submicrometer crystal size.
- Lee, Song-Ho,Shin, Chae-Ho,Hong, Suk Bong
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- Kinetic scheme of homogeneous acid-catalyzed transformation of isopentenols
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The reactions occurring in an equilibrium mixture of 3-methyl-1-buten-3-ol and 3-methyl-2-buten-1-ol in 24-49 percent aqueous solutions of H2SO4 yield isoprene, 3-methyl-3-buten-1-ol, isobutylene, formaldehyde, 3-methylbutane-1,3-diol.Isobutylene is rapidly hydrated to give 2-methylpropan-2-ol.The presence of formaldehyde in the reaction mixture indicates that the transformations involve the reverse Prins reaction.On the basis of experimental and literature data, two most probable reactions were suggested.
- Ryabova, R. S.,Osipova, G. F.,Travin, S. O.
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- Rate coefficients of hydroxyl radical reaction with dimethyl ether and methyl tert-butyl ether over an extended temperature range
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Rate coefficients of the reaction of hydroxyl (OH) radicals with CH3OCH3 (k1) and CH3OC(CH3)3 (k2) over an extended temperature range are reported. Measurements were performed using a laser photolysis-laser-induced fluorescence technique under slow flow conditions at a total pressure of 740±10 Torr. Arrhenius plots of the data exhibited significant curvature and were fitted in the form of k(T) = ATB exp(-C/T). The resulting modified Arrhenius expressions (error limits ±2σ) that best described these extended temperature measurements and prior low-temperature measurements were (in units of cm3 molecule-1 s-1) k1(295-650 K) = (1.05±0.10)×10-17T2.0 and exp[(328±32)/T] and k2(293-750 K) = (1.15±0.11)×10-17T2.04 exp-[(266±41)/T]. Comparison of our measurements for k1 with previous, overlapping low-temperature measurements indicated generally good agreement. Our measurements for k2, although consistent with previous room temperature measurements, exhibited a larger temperature dependence than previously reported. High-temperature oxidation mechanisms for these oxygenated fuel components are proposed. Support for the mechanisms is presented in the form of product analysis studies in high-temperature tubular flow reactors. For CH3OC(CH3)3, these studies suggest that H abstraction from the tert-butyl group is an important high-temperature oxidation pathway.
- Arif,Dellinger,Taylor
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- A Kinetic Study of the Thermal Decarboxylation of α,α-Difluoro β-Lactones
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The rates of thermolysis of α,α-difluoro β-lactones 1, leading to CO2 and 1,1-difluoro olefins, have been obtained in the gas phase and in solution, and the activation parameters are reported. Ab initio calculations on the fluoro and nonfluorinated βlactone systems are also reported. The gas-phase kinetic and theoretical results are discussed in terms of a probable concerted, asynchronous, nonpolar mechanism, whereas the solution kinetics, which include extensive solvent effect studies, are discussed in terms of a polar mechanism which probably involves formation of a zwitterionic intermediate.
- Ocampo, Rogelio,Dolbier Jr., William R.,Bartberger, Michael D.,Paredes, Rodrigo
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- Catalytic Isomerisation of But-1-ene to 2-Methylpropene over Solid Acids: Comparison between DAF-1 and other Shape-selective Magnesium-containing Aluminophosphates and Aluminosilicates
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Although DAF-1 is a superior isomerisation catalyst at lower temperatures -1> both its activity and its selectivity, as well as its longevity, are inferior to those of H+-ferrierite and H+-Theta-1- in the range 350-400 deg C: the performance of MALPO-5, -11 and of -36 (M = Mg) is much poorer than that of DAF-1.
- Natarayan, Srinivasan,Wright, Paul A.,Thomas, John Meurig
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- Production of isobutylene from acetone over micro–mesoporous catalysts
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The production of isobutylene from acetone over micro–mesoporous catalysts with different mesopore contents, which have been prepared using hydrothermal recrystallization of mordenite (MOR) zeolite modified with cesium acetate by incipient wetness impregnation, has been studied. It has been shown that cesium is inserted into the cation positions during the modification, at the same time the number of Br?nsted acid sites in the samples decreased. It has been found that an increase in the content of mesopores in the catalyst leads to an increase in the initial rates of acetone conversion and isobutylene formation as a result of removing diffusion limitations. Br?nsted acid sites have been shown to be preferable for the selective production of isobutylene from acetone. Micro–mesoporous materials operate more stably as compared to microporous materials.
- Ponomareva,Mal’tseva,Maerle,Rodionova,Pavlov,Dobryakova,Belova,Ivanova
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- Kinetics, Products, and Mechanisms of Reaction of tert-Butyl Chloride with Sodium Methoxide in Methanol and Dimethyl Sulfoxide/Methanol Solvents
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The rate of reaction of tert-butyl chloride with methanolic sodium methoxide shows little variation with base concentration up to 1 mol/L, but the presence of MeONa causes the product composition to shift strongly toward 2-methylpropene.What mechanisms prevail is uncertain; one possibility is that as increases the E2 mechanism participates to a small but increasing extent while E1-SN1 solvolysis continues at a nearly constant rate.When the solvent is enriched in dimethyl sulfoxide, the overall rate increases robustly with in nonlinear fashion, with increasing slope, and the product is almost entirely the alkene.
- Bunnett, Joseph F.,Migdal, Cyril A.
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- The Elimination Kinetics of 2-Bromo-3-Methylbutyric Acid in the Gas Phase
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The kinetics of 2-bromo-3-methylbutyric acid in the gas phase was studied over the temperature range of 309.3 - 357.0 deg C and pressure range of 15.5 - 100.0 torr.This process, in seasoned static reaction vessels and in the presence of the free radical i
- Chuchani, Gabriel,Dominguez, Rosa M.
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- Oxidative dehydrogenation of isobutane catalyzed by an activated carbon fiber cloth exposed to supercritical fluids
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Modifications that supercritical fluids promote in the surface chemistry of carbon materials are scarcely investigated. Due to this lack of knowledge, carbon materials exposed to supercritical fluids have not been tested in any catalytic application. Here, we present the oxidative dehydrogenation of isobutane catalyzed by an activated carbon fiber cloth previously exposed to supercritical carbon dioxide, supercritical water and nitric acid. The role of carbonyl-quinone groups as active sites is confirmed by their direct correlation with catalytic activity. The ability of the active sites to produce isobutene is hindered by the presence of acidic groups. Supercritical treatments develop microporosity, while removing acidic oxygen surface groups and incorporating carbonyl-quinone groups, so they are appropriate methods to develop efficient carbon catalysts for this reaction. Coke deposits formed during reaction modify the surface chemistry and porosity of the catalysts. Samples presenting high surface areas are deactivated by coke deposition more slowly. Thanks to it, fibers exposed to supercritical water showed the best performance.
- Martin-Sanchez, Nicolas,Soares,Pereira, Manuel F.R.,Sanchez-Montero, M.Jesus,Figueiredo, José L.,Salvador, Francisco
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- Alternative synthetic strategies for new drug candidates. The thermolysis reaction of N-(benzyl)-N′-(tert-butoxycarbonyl)sulfamide to yield benzylsulfamide
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The hydrolysis of one sulfamide derivative under conventional conditions and under thermolysis reaction has been investigated. Comparison between these techniques revealed advantages in the use of thermal decomposition reaction to obtain sulfamides, due to the easy elimination of gaseous by-products produced in the reaction.
- Lick,Gavernet,Bruno-Blanch,Ponzi
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- Enhancement of catalytic wet air oxidation of tert-amyl methyl ether by the addition of Sn and CeO2 to Rh/Al2O3 catalysts
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The Rh and Rh-Sn supported catalyst on γ-Al2O3 and γ-Al2O3-CeO2 (loading 1, 5 and 20 Ce wt%) were characterized by means of electron microscopy (TEM), temperature programmed reduction (TPR), Fourier transformed infrared of CO adsorption (FTIR-CO) and X-ray photoelectron spectroscopy (XPS). The catalysts were tested in the catalytic wet air oxidation of an aqueous solution of 227 ppm of TAME and 1 g/L of catalyst (120 °C and 10 bar of oxygen partial pressure). The rhodium monometallic catalysts showed an increase in the activity with the load of cerium oxide in the catalyst. The coexistence of Rh°/Rh δ+ and Ce4+/Ce3+ redox couples facilitates the activation of TAME and hence the catalytic activity and selectivity to mineralization. The addition of Snδ+ enhances the activity and selectivity; this is explained by assuming that Sn δ+ acts as Lewis acid sites trapping the TAME molecules for further oxidation on rhodium metal particles.
- Cuauhtémoc,Del Angel,Torres,Angeles-Chavez,Navarrete,Padilla
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- Direct conversion of bio-ethanol to propylene in high yield over the composite of In2O3 and zeolite beta
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A series of In2O3-beta composites with different contents of zeolite beta were prepared by the deposition-precipitation method, followed by calcination at 700 °C, and their catalytic performance in the conversion of ethanol to propylene (ETP) was investigated. The physicochemical properties of the as-synthesized materials were characterized by XRD, N2 adsorption, SEM, NH3-TPD, CO2-TPD and a probe reaction. The combination of In2O3 and zeolite beta improves the propylene yield significantly. The optimal result was observed for the composite with a beta content of 20-50%, which gave ca. 50% yield of propylene. The role of beta in the In2O3-beta composite catalyst is to promote the conversion of the intermediate of acetone to propylene via an additional reaction pathway, which accounts for the superior propylene yield of the In2O3-beta composite in comparison with In2O3 (ca. 32%). The proximity of these two components (In2O3 and zeolite beta) plays a crucial role in achieving a high yield of propylene for the ETP reaction.
- Xue, Fangqi,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
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- Collisional Energy Transfer in the Multiphoton Decomposition of tert-Butyl Methyl Ether
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The multiphoton decomposition (MPD) of tert-butyl methyl ether was studied with a 100-ns pulsed CO2 laser operating on the 9R(20) line and at a fluence of 12 J/cm2.For TBME pressures up to 2.7 kPa, MPD gave the following products: 2-methylpropene (TMP), methanol, 2-methyl-2-butene, acetone, methane, hydrogen, ethene, and ethane.The products result from reactions among the species produced through two channels: (1) TMP + methanol; (2) acetone + 2 CH3.A collision-dependent reaction scheme is presented to explain the pressure dependence of the MPD.In this instance, significant energy transfer between two laser-excited TBME molecules occurs before decomposition takes place.The decomposition products deactivate excited TBME molecules and reduce subsequent decomposition.
- McRae, Glenn A.,Lee, Paul E.,McAlpine, Robert D.
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- CHLOROTRIMETHYLSILANE-PHENOL AS A MILD DEPROTECTION REAGENT FOR THE TERT-BUTYL BASED PROTECTING GROUPS IN PEPTIDE SYNTHESIS
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Efficient deprotection of the tertbutyl urethane group by 1 M Me3SiCl- 1 M and 3 M-phenol reagents is described.
- Kaiser, Emil,Tam, James P.,Kubiak, Teresa M.,Merrifield, R. B.
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- SELECTIVE FORMATION OF ISO-BUTENE FROM CARBON MONOXIDE AND HYDROGEN OVER ZIRCONIUM OXIDE CATALYST
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Iso-butene was selectively produced from CO-H2 reaction over ZrO2 catalyst under moderate conditions (0.5-21 atm, 300-450 deg C).
- Maehashi, Tatsuichi,Maruya, Ken-ichi,Domen, Kazunari,Aika, Ken-ichi,Onishi, Takaharu
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- Catalytic dehydrogenation of isobutane over a Ga2O3/ZnO interface: Reaction routes and mechanism
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In this work, physical mixtures of ZnO and Ga2O3, even with a small amount of Ga2O3, were found to exhibit greatly enhanced catalytic performance for isobutane dehydrogenation compared to their individual components, namely solely ZnO or Ga2O3. The activity test results under different packing patterns indicated that, the interface between the two component oxides played a crucial role in improving the dehydrogenation performance. Moreover, consistent with the highest dehydrogenation reactivity, the largest activation energy for isobutane desorption over ZnO-Ga2O3 was determined using an isobutane-TPD test. The observed synergistic effect of ZnO and Ga2O3 could be understood as being that, Lewis acid sites provided by Ga2O3 promoted the heterolytic cleavage of C-H bonds in isobutane over ZnO, thereby increasing the isobutane conversion. On the surface of ZnO-Ga2O3, a double-site adsorption of isobutane was further speculated through FT-IR spectra analysis, and one-step decomposition was probably the actual reaction pathway of isobutane. In addition, from understanding that catalyst deactivation was caused by highly graphitized coke deposition, the deactivated catalyst was regenerated through air combustion, and good catalyst stability was demonstrated through continuous reaction-regeneration cycles.
- Wang, Guowei,Li, Chunyi,Shan, Honghong
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- Praseodymium-containing catalysts for oxidative dehydrogenation of organic compounds
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A method is developed for incorporating praseodymium into magnesium–aluminum hydrotalcites, which are precursors for oxide catalysts for oxidative dehydrogenation (ODH) of alkanes. Oxide catalyst samples that contain praseodymium and various combinations of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium are prepared. The catalytic properties of the prepared catalysts in ethane, propane, and butane ODH reactions are studied. Into some of our studied multicomponent catalysts, the incorporation of praseodymium enhances the reaction selectivity and increases yields of desired products.
- Krasnobaeva,Belomestnykh,Nosova,Kondakov,Elizarova,Danilov
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- [(≡SiO)TaV (=CH2)Cl2], the first tantalum methylidene species prepared and identified on the silica surface
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A novel surface tantalum methylidene [(≡SiO)TaV (=CH 2)Cl2] was obtained via thermal decomposition of the well-defined surface species [(≡SiO)TaVCl2Me 2]. This first surface tantalum methylidene ever synthesized has been fully characterized and the kinetics of the a-hydrogen abstraction reaction has also been investigated in the heterogeneous system.
- Chen, Yin,Callens, Emmanuel,Abou-Hamad, Edy,Basset, Jean-Marie
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- Cyanoketene and Iminopropadienones
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Cyanoketene (8) is generated in high yields on flash vacuum thermolysis (FVT) of suitably substituted Meldrum's acid derivatives (5-[(alkylamino)(methylthio or alkylamino)methylene]-2,2-dimethyl-1,3-dioxane-4,6-diones) (3e-j), and also on FVT of cyanoacetic acid derivatives 9e,f,g,j,k,m. The major reaction pathway from 3 proceeds via ketenimines 6 and (alkylimino)propadienones 7, the latter undergoing a retro-ene reaction to 8. A minor pathway is via imidoylketenes 4e,h and oxoketenimines 5e,h, which undergo retro-ene reactions to 9. All intermediates were characterized by Ar matrix FTIR and tandem mass spectrometry (collisional activation MS). Trapping of 4, 5, and 8 with nucleophiles is also reported. The preference of 1,3-X shifts over 1,5-H shifts in imidoylketenes 12 (X = SMe or NMe2) is corroborated by the calculated activation barriers. Neat cyanoketene is highly reactive, reacting at or below 80 K, and this is attributed to the availability of a low-lying ketene LUMO. The IR spectrum of cyanoketene (Ar, 14 K) is dominated by two absorptions at 2163 (s; C=C=O) and 2239 (w; CN) cm-1 in excellent agreement with density functional (B3-LYP/6-31G*) and ab initio (QCISD/6-31G*) calculations.
- Moloney, Daniel W. J.,Wong, Ming Wah,Flammang, Robert,Wentrup, Curt
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- Selective Isomerization of Butene to Iso-Butene
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Selective isomerization of butene to iso-butene has been studied with pure and variously modified alumina as catalysts.Results can be self-consistently eplained by concluding that (i) the molecular mechanism operates and requires Lewis acid sites, the presence and quality of which can be modulated by heat treatment in hydrogen, by surface modification with halogens, and by application of certain catalytic poisons, and (ii) the bimolecular mechanism is related to the Broensted acid sites and is stimulated, as expected, by increased pressure of n-butene.
- Cheng, Zheng Xing,Ponec, Vladimir
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- Electrolytic-Reduction of tert-Butyl Bromide at Mercury Cathodes in Dimethylformamide
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A polarogram or cyclic voltammogram for reduction of tert-butyl bromide at mercury in dimethylformamide containing a tetraalkylammonium salt exhibits two waves, signaling stepwise generation of the tert-butyl radical and carbanion.Electrolyses of the alkyl bromide at a mercury pool cathode and at potentials corresponding to the first wave produce isobutane (40-43percent), isobutylene (43-45percent), and 2,2,3,3-tetramethylbutane (9-10percent).Experiments with perdeuterated tert-butyl bromide have revealed that the first two products arise via disproportionation of tert-butyl radicals, whereas the third compound is formed by combination of radicals.At potentials on the second wave for tert-butyl bromide, electrolyses in dimethylformamide containing either tetramethylammonium or tetra-n-butylammonium perchlorate yield equal quantities of isobutane (47-50percent) and isobutylene (47percent), but little 2,2,3,3-tetramethylbutane (1percent) is formed; interestingly, when tetraethylammonium perchlorate is the electrolyte, the products are isobutane (55percent), isobutylene (30percent), pivalaldehyde (14percent), and 2,2,3,3-tetramethylbutane (1percent).Electrolyses done in the presence of deuterated reagents have demonstrated that electrogenerated tert-butyl carbanions are protonated by water and, to a lesser extent, tetramethylammonium and tetraethylammonium cations to yield isobutane.Hydroxide ion, formed when water is deprotonated by the alkyl carbanion, attacks unreduced tert-butyl bromide to give isobutylene.
- Vieira, Kenneth L.,Peters, Dennis G.
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- Selective Oxidative Dehydrogenation of Isobutane over a Y2O3-CeF3 Catalyst
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The multi-valence anion modified complex catalyst Y2O3-CeF3 was found to be selective for the oxidative dehydrogenation of isobutane to isobutene at a relatively high conversion.
- Zhang, Wei-De,Tang, Ding-Liang,Zhou, Xiao-Ping,Wan, Hui-Lin,Tsai, K. R.
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- Zirconium-SAPO-11: The peculiar effect of zirconium addition on the catalytic properties for n-butene isomerization
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SAPO-11 and Zr-SAPO-11 solids were synthesized by hydrothermal methods and characterized. Zirconium is not incorporated in the SAPO-11 framework but is localized, at least partially, in the pores of the solid, inducing a partial pore blockage. When used in n-butene isomerization, both solids are active and selective but Zr-SAPO-11 exhibited higher isobutene selectivity as compared to SAPO-11. This improved isobutene selectivity for Zr-SAPO-11 catalyst is attributed to the presence of zirconium in the pores causing an increased shape selectivity.
- Meriaudeau,Tuan,Hung,Lefebvre,Nguyen
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- EXTRACTION OF STANDARD HELMHOLTZ FUNCTIONS FROM AFFINITY RATE DATA
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An extrapolation procedure to extract standard Helmholtz functions from empirical kinetic data without reference to reaction mechanisms has been developed using an analytical description of the affinity decay rate.
- Garfinkle, Marvin
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- Mechanism of Elimination Reactions. 38. Why Is the Effect of Successive β-Alkyl Substitution on the Rates of Elimination from Quaternary Ammonium Salts Nonadditive?
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Possible reasons are examined for the nonadditivity of the effect of successive β-methyl substitution on the rates of elimination reactions of quaternary ammonium salts.The temperature dependences of the deuterium isotope effects in E2 reactions of R1R2NMe2+ show that tunneling is not a significant source of nonadditivity.Neither is a change of gross mechanism or stereochemistry, for studies with C4H9CHDCHDNMe3+ and C4H9(CH3)CHCHDNMe3+ show the reactions to be very predominantly (>88percent) anti-E2 in both cases.Secondary tritium isotope effects with R1R2CHCHTNMe3+ increase, however in the order ethyl (1.108 +/- 0.002), propyl (1.150 +/- 0.015), isobutyl (1.216 +/- 0.012).This result suggests increasing rehybridization at the α-carbon in the transition state and therefore a shift toward less E1cB and more central-E2 character.Since methyl substitution is expected to favor a developing double bond, the much smaller rate-depressing effect of the second β-methyl is accounted for by such a shift in transition-state character.
- Wu, Shune-Long,Tao, Yu-Tai,Saunders, William H.
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- The Study of CrOx-Containing Catalysts Supported on ZrO2, CeO2, and CexZr(1–x)O2 in Isobutane Dehydrogenation
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Olefin hydrocarbons are valuable raw materials for petrochemical and polymer manufacturing. Highly effective, but toxic chromium-containing catalytic materials are the most widely used catalysts to obtain olefins in industry. In this regard, the urgent challenge to increase the efficiency of oil processing is to develop the catalysts with low content of harmful active component. In the present study, the catalysts with low chromium content (1 theoretical monolayer = 5 Cr atoms per nm2 of support) were synthesized by incipient wetness impregnation of the supports (Al2O3, ZrO2, CeO2, and CexZr(1–x)O2). The samples obtained were characterized by low-temperature nitrogen adsorption, X-ray diffraction and H2-temperature-programmed reduction methods. The catalytic properties of the catalysts were tested in isobutane dehydrogenation reaction. It was shown that the state of chromium on the surface is different over different supports. For the CrOx/CeO2 catalyst, the formation of Cr2O3 particles with low activity in the dehydrogenation reaction was observed. For other samples, a highly disperse X-ray amorphous state of chromium was characteristic. The catalyst based on CexZr(1–x)O2 was the most active in isobutane dehydrogenation reaction due to possible stabilization of chromium as Cr(V) state.
- Bugrova,Mamontov
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- Enthalpies of formation of 2-methyl-2-ethoxypropane and 2-ethyl-2-ethoxypropane from equilibrium measurements
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The equilibria for the synthesis of C2H5OC(CH3)3 (A) and C2H5OC(CH3)2(C2H5) (B) from C2H5OH (C) and CH2:C(CH3)2 (D) or CH3CH:C(CH3)2 (E) in the liquid phase were investigated at temperatures from 313 K to 412 K.On the basis of experimental equilibrium constants found for n(C)/n(D) or n(C)/n(E) >/= 4, the following values were obtained for ΔrH0m/(kJ * mol-1) and ΔrS0m/(J * K-1 * mol-1): (C + D = A), -(35.45 +/- 1.94) and -(82.37 +/- 5.99); (C + A = B), -(34.13 +/- 0.81) and -(87.82 +/- 2.18).The following values of ΔfH0m(298.15 K)/(kJ * mol-1) have been derived: C2H5OC(CH3)3(l), -(350.8 +/- 2.6); C2H5OC(CH3)2(C2H5)(l), -(379.8 +/- 1.4).
- Sharanov, K. G.,Rozhnov, A. M.,Korol'kov, A. V.,Karaseva, S. Y.,Miroshnichenko, E. A.,Korchatova, L. I.
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- GAS PHASE THERMOLYSIS OF N-(TERT-BUTYLTHIO)ALLYLAMINE AND N-(TERT-BUTYLTHIO)DIETHYLAMINE
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The title sulphenamides were pyrolysed in a stirred-flow reactor at temperatures of 310-410 deg C, pressures of 8-15 Torr and residence times of 0.4-2 s using toluene as the carrier gas.N-(tert-Butylthio)allylamine formed 73 +/- 4percent isobutene, 23 +/- 3percent propene and N-allylthiohydroxylamine.The first-order rate coefficients for the formation of isobutene and propene, respectively,followed the Arrhenius equations kC4(s-1) = 1012.52 +/- 0.36 exp(-163 +/- 5 kJ mol-1 RT) and kC3(s-1) = 1010.99 +/- 0.29 exp(-151 +/- 4 kJ mol-1 RT).N-(tert-Butylthio)diethylamine gave 97 +/- 1 percent isobutene, 1.9 +/- 0.4 percent isobutane and N,N-diethylthiohydroxylamine.The first-order rate coefficients for isobutene elimination followed the Arrhenius equation k(s-1) = 1013.45 +/- 0.24 exp(-164 +/- 3 kJ mol-1 RT).The formation of the products is interpreted in terms of an elimination reaction with a unimolecular, four-centered, cyclic transition state.The reactivity of these sulphenamides was found to be much higher than that of previously studied alkyl or aryl tert-butyl sulphides and disulphides.
- Martin, Gonzalo,Ascanio, Julian,Rodriguez, Jesus
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- Kinetics of liquid phase synthesis of ethyl tert-butyl ether from tert-butyl alcohol and ethanol catalyzed by β-zeolite supported on monolith
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This paper compared the performance of β-zeolite and Amberlyst-15 catalysts on a liquid phase synthesis of ethyl tert-butyl ether (ETBE) from ethanol (EtOH) and tert-butyl alcohol (TBA) β-Zeolite was synthesized and deposited on monolith support. Its structure was confirmed by an XRD measurement and its composition was analyzed by an XRF measurement. It was found that even though the catalytic activity of β-zeolite was lower than that of Amberlyst-15, the selectivity of ETBE was much higher than that of Amberlyst-15, resulting in almost the same level of ETBE yield. The dehydration of TBA to isobutene (IB) was the major side reaction. The kinetic study of the reaction catalyzed by β-zeolite supported on monolith was carried out by using a semibatch reactor. The effect of external mass transfer was investigated by varying stirring speeds. The activity-based rate expressions were developed taking into account of water inhibition. Three temperature levels of 323, 333, and 343 K were performed in the study to obtain the parameters in the Arrhenius's equation and the Van't Hoff's equation.
- Assabumrungrat,Kiatkittipong,Sevitoon,Praserthdam,Goto
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- Bulk binary ZrO2-based oxides as highly active alternative-type catalysts for non-oxidative isobutane dehydrogenation
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Bulk binary ZrO2-based oxides efficiently catalyse non-oxidative dehydrogenation of isobutane to isobutylene. Their activity strongly depends on the kind of second metal oxide. So designed CrZrOx showed superior activity to industrially relevant catalysts with supported Pt or CrOx species. It was also stable under alternating dehydrogenation and oxidative regeneration cycles over ca. 110 h under different reaction conditions between 550 and 600 °C.
- Otroshchenko, Tatyana,Radnik, J?rg,Schneider, Matthias,Rodemerck, Uwe,Linke, David,Kondratenko, Evgenii V.
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- METHOD FOR DEHYDRATING ALCOHOLS TO OBTAIN OLEFINS, INVOLVING A STEP OF CATALYST SELECTIVATION
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The invention relates to a process for dehydrating alcohols to olefins, comprising a reaction step and a catalyst selectivation step.
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Paragraph 0055-0077
(2021/03/19)
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- Effect of the pore structure of an active alumina catalyst on isobutene production by dehydration of isobutanol
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An alumina catalyst was prepared by mixing and pinching with pseudo-boehmite, and the catalyst was reamed with polyethylene glycol. The catalysts prepared were characterized by means of XRD, mercury injection and NH3-TPD, and the dehydration properties of the catalysts prepared with different amounts of reamer were evaluated in a 10 mL fixed bed reactor with 5% water as a raw material. The results showed that the addition of reamer did not affect the crystal structure and the amount of acid of the catalyst. With the increase of the amount of reamer, the pore volume of the catalyst increased continuously, the number of large pores increased, the conversion rate of isobutanol increased, and the selectivity of isobutene remained basically unchanged. When the amount of reamer is 30%, the isobutanol conversion rate is the best. The isobutanol conversion rate and the isobutene selectivity were 97% and 93% respectively under the conditions of 330 °C, 0.1 MPa and 12 h?1air velocity of the body liquid.
- Tian, Kaige,Li, Qin,Jiang, Weili,Wang, Xiaosheng,Liu, Shicheng,Zhao, Yapeng,Zhou, Guanglin
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p. 11952 - 11958
(2021/04/06)
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- Insights into the doping effect of rare-earth metal on ZnAl2O4 supported PtSn catalyzed isobutane dehydrogenation
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Isobutane dehydrogenation is a vital route for the production of isobutene, an important substance for methyl tert-butyl ether. However, the reaction is typically performed at relatively low pressure and high temperature, resulting in a facilitated coke formation. Here, we used rare-earth metals (Y, La, Ce) as dopants to modify the ZnAl2O4 support and studied their effects on Pt-Sn catalyzed dehydrogenation of isobutane. Combining the experimental and theoretical results, it is demonstrated that while Y and La tend to incorporate into the matrix of ZnAl2O4, separate CeO2 phase could be easily formed on ZnAl2O4 surface, leading to a decrease in both amount and strength of the Lewis acid sites. And for the La-ZnAl2O4, because of the large local deformation, oxygen vacancy can be readily formed, and results in a lot acid sites in the subsurface layer available for reactions. Deactivation rates of the catalysts in isobutane dehydrogenation is found to linearly correlate with the Lewis acid amounts over the modified supports. Compared with the catalysts of Pt-Sn/ZnAl2O4, Pt-Sn/La-ZnAl2O4 and Pt-Sn/Y-ZnAl2O4, Pt-Sn/Ce-ZnAl2O4 exhibits superior catalytic performance due to the low coke contents and high Pt dispersion. These results may provide additional insights on the design and optimization of isobutane dehydrogenation catalysts by tailoring the composition and structure of oxide supports.
- Liu, Jianfeng,Zhou, Wei,Jiang, Dongyu,Wang, Dong,Wu, Wenhai,Wang, Yue,Ma, Xinbin
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- Stabilizing Oxygen Vacancies in ZrO2by Ga2O3Boosts the Direct Dehydrogenation of Light Alkanes
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The conversion of light alkanes to olefins (e.g., ethylene, propylene, or butylene) is crucial to the chemical industry. ZrO2 with oxygen vacancies has recently been regarded as a promising catalyst for the direct dehydrogenation of light alkanes. However, the intrinsic mechanism of the effect of oxygen vacancies on catalytic performance has not been completely understood yet, and ZrO2 without promoters generally displays poor activity toward the direct dehydrogenation of light alkanes. In this work, we demonstrate that the oxygen vacancies in ZrO2 can be poisoned by H atoms during the dehydrogenation of light alkanes, and we report a strategy for stabilizing the oxygen vacancies in ZrO2 by Ga2O3. Experimental results and theoretical calculations indicate that ZrO2 with oxygen vacancies is responsible for dehydrogenation, while Ga2O3 prevents the poisoning of oxygen vacancies by dissociated hydrogen atoms which, in the absence of the Ga2O3 component, blocks further dehydrogenation. Consequently, the optimal Zr0.26Ga1 catalyst exhibits superior propane dehydrogenation performance to the industrial Pt-Sn catalyst, the state-of-the-art catalyst for the direct dehydrogenation of light alkanes. We anticipate this work may shed light on both the fundamental research of catalysis and the chemical industry.
- Cao, Muhan,Hu, Huicheng,Li, Youyong,Lifshitz, Yeshayahu,Lin, Haiping,Liu, Lijia,McLeod, John,Sham, Tsun-Kong,Tang, Zeyuan,Wang, Xuchun,Wu, Linzhong,Xu, Yong,Yang, Di,Zhang, Qiao
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p. 10159 - 10169
(2021/08/24)
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- Synthesis and catalytic application of nanorod-like FER-type zeolites
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Nanosize dimensions have an important impact on zeolite properties and catalytic performance in particular. Herein, we develop a direct synthesis route to obtain a nanosized nanorod-like ferrierite (FER) zeolite with the assistance of ammonium fluoride (NH4F) and employing a conventional structure-directing agent (pyrrolidine). The resultant nanorod-like FER zeolite crystals exhibit a greatly reduced diffusion path along the c-axis. The physicochemical properties of nanorod-like FER and its conventional micronsized plate-like counterpart were analyzed by N2 adsorption-desorption, 27Al, 1H, 29Si MAS NMR, NH3-TPD, and in situ D3-acetonitrile and pyridine adsorption followed by FTIR. The nanorod-like FER zeolite possesses superior characteristics in terms of a larger external area, better accessibility to the acid sites, and a larger number of pore mouths per unit crystal surface than the micron-sized counterpart synthesized without NH4F. The improved properties provide the nanorod-like FER zeolite with high selectivity and low deactivation rates in 1-butene skeletal isomerization. The thermogravimetry analysis (TGA) of the coke amounts revealed a better capability of coke tolerance of the nanorod-like FER zeolite. The in situ ultraviolet-visible (UV/Vis) and Fourier transform infrared spectroscopy (FTIR) spectroscopy investigations of the organic intermediates formed on FER zeolite catalysts during the catalytic reaction further verified the enhanced catalytic activity and stability of the nanorod-like FER zeolite.
- Dai, Weijiong,Deng, Xin,Guan, Naijia,Li, Landong,Ruaux, Valérie,Tai, Wenshu,Valtchev, Valentin,Wu, Guangjun
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p. 24922 - 24931
(2021/11/27)
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- Method for isobutylene from tert-butanol
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In the dehydration reaction of tert - butanol, the specific surface area is 30m. 2 Zirconia oxide (ZrO) above/g2 Using a solid acid catalyst. Provided is a process for preparing isobutylene which can show high conversion of tert - butanol and high selectivity to isobutylene while inhibiting oligomerization and side reactions of isobutylene. A method for producing isobutylene using tert - butanol is provided to obtain high purity isobutylene without adding a separate distillation process with high conversion of tert-butanol and isobutylene.
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Paragraph 0031-0045; 0054
(2021/07/06)
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- Aqueous Microdroplets Capture Elusive Carbocations
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Carbocations are short-lived reactive intermediates in many organic and biological reactions that are difficult to observe. This field sprung to life with the discovery by Olah that a superacidic solution allowed the successful capture and nuclear magnetic resonance characterization of transient carbocations. We report here that water microdroplets can directly capture the fleeting carbocation from a reaction aliquot followed by its desorption to the gas phase for mass spectrometric detection. This was accomplished by employing desorption electrospray ionization mass spectrometry to detect a variety of short-lived carbocations (average lifetime ranges from nanoseconds to picoseconds) obtained from different reactions (e.g., elimination, substitution, and oxidation). Solvent-dependent studies revealed that aqueous microdroplets outperform organic microdroplets in the capture of carbocations. We provide a mechanistic insight demonstrating the survival of the reactive carbocation in a positively charged aqueous microdroplet and its subsequent ejection to the gas phase for mass spectrometric analysis.
- Kumar, Anubhav,Mondal, Supratim,Banerjee, Shibdas
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supporting information
p. 2459 - 2463
(2021/02/16)
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- HYDROTHERMAL PRODUCTION OF ALKANES
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Synthesizing an alkane includes heating a mixture including an alkene and water at or above the water vapor saturation pressure in the presence of a catalyst and one or both of hydrogen and a reductant, thereby hydrogenating the alkene to yield an alkane and water, and separating the alkane from the water to yield the alkane. The reductant includes a first metal and the catalyst includes a second metal.
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Paragraph 0022
(2021/04/17)
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- Mechanism and Kinetics of Acetone Conversion to Isobutene over Isolated Hf Sites Grafted to Silicalite-1 and SiO2
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Isolated hafnium (Hf) sites were prepared on Silicalite-1 and SiO2 and investigated for acetone conversion to isobutene. Characterization by IR, 1H MAS NMR, and UV-vis spectroscopy suggests that Hf atoms are bonded to the support via three O atoms and have one hydroxyl group, i.e, (SiO)3Hf-OH. In the case of Hf/Silicalite-1, Hf-OH groups hydrogen bond with adjacent Si-OH to form (SiO)3Hf-OH···HO-Si complexes. The turnover frequency for isobutene formation from acetone is 4.5 times faster over Hf/Silicalite-1 than Hf/SiO2. Lewis acidic Hf sites promote the aldol condensation of acetone to produce mesityl oxide (MO), which is the precursor to isobutene. For Hf/SiO2, both Hf sites and Si-OH groups are responsible for the decomposition of MO to isobutene and acetic acid, whereas for Hf/Silicalite-1, the (SiO)3Hf-OH···HO-Si complex is the active site. Measured reaction kinetics show that the rate of isobutene formation over Hf/SiO2 and Hf/Silicalite-1 is nearly second order in acetone partial pressure, suggesting that the rate-limiting step involves formation of the C-C bond between two acetone molecules. The rate expression for isobutene formation predicts a second order dependence in acetone partial pressure at low partial pressures and a decrease in order with increasing acetone partial pressure, in good agreement with experimental observation. The apparent activation energy for isobutene formation from acetone over Hf/SiO2 is 116.3 kJ/mol, while that for Hf/Silicalite-1 is 79.5 kJ/mol. The lower activation energy for Hf/Silicalite-1 is attributed to enhanced adsorption of acetone and formation of a C-C bond favored by the H-bonding interaction between Hf-OH and an adjacent Si-OH group.
- Bell, Alexis T.,Lu, Peng,Lund, Alicia,Qi, Liang,Zhang, Yanfei
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p. 8352 - 8366
(2021/06/27)
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- Alkylation of Phenol with tert-Butanol in a Draining-Film Reactor
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The alkylation of phenol with tert-butanol in a displacement draining-film reactor on a heterogeneous catalyst, Beta zeolite, was evaluated. Optimum process conditions ensuring the maximal p-tert-butylphenol yield were determined: phenol:tert-butanol molar ratio (3–3.5):1, superficial liquid velocity 1.0–1.5 m3 m–2 h–1, and temperature 100°C–110°C. A procedure ensuring 100% conversion of tert-butanol and isobutylene (a by-product formed from tert-butanol) was observed.
- Maksimov, A. L.,Mel’chakov, I. S.,Terekhov, A. V.,Zanaveskin, L. N.
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p. 569 - 575
(2021/07/26)
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- Ni-Catalyzed Reductive Allylation of α-Chloroboronates to Access Homoallylic Boronates
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The transition-metal-catalyzed allylation reaction is an efficient strategy for the construction of new carbon-carbon bonds alongside allyl or homoallylic functionalization. Herein we describe a Ni-catalyzed reductive allylation of α-chloroboronates to efficiently render the corresponding homoallylic boronates, which could be readily converted into valuable homoallylic alcohols or amines or 1,4-diboronates. This reaction features a broad substrate scope with good functional group compatibility that is complementary to the existing methods for the preparation of homoallylic boronates.
- Lou, Yixian,Qiu, Jian,Yang, Kai,Zhang, Feng,Wang, Chenglan,Song, Qiuling
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supporting information
p. 4564 - 4569
(2021/06/28)
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- PROCESS AND SYSTEM TO MAKE SUBSTITUTED LACTONES
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A process for oxidizing iso-butane with oxygen to produce t-butyl hydroperoxide and t-butyl alcohol; dehydrating at least a portion of the t-butyl alcohol to produce di-tert-butyl ether and isobutylene; epoxidizing at least a portion of the isobutylene with the t-butyl hydroperoxide to produce isobutylene oxide and t-butyl alcohol; and carbonylating at least a portion of the isobutylene oxide with carbon monoxide to produce pivalolactone.
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Paragraph 0052; 0054
(2021/02/05)
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- Tuning supported Ni catalysts by varying zeolite Beta heteroatom composition: effects on ethylene adsorption and dimerization catalysis
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The influence of zeolite heteroatom composition on the electron density and catalytic activity of a supported Ni cation is examined. Ni-[X]-Beta catalysts, where X = Al, Ga, Fe, or dealuminated, were synthesized and characterized with probe molecule adsorption with FTIR spectroscopy and C2H4dimerization catalysis. It was observedviaCO adsorption that supported Ni cations were increasing in electron density in the order: [Fe] > [Ga] > [Al]. C2H4dimerization activity increased with increasing electron density of the Ni cation. Despite similarities in reported acid site strength, the acid sites on [Fe]-Beta in this work had significantly lower activity than those on [Ga]-Beta for the skeletal isomerization of linear butenes as well as C2H4dimerization. Introducing H2as a reactant resulted in a decrease in dimerization activity for Ni-[Al]-Beta and Ni-[Ga]-Beta but an increase for Ni-[Fe]-Beta. The selectivity and activity of Ni-[DeAl]-Beta changed dramatically with the introduction of H2, which subsequently converted all C2H4withca.100% selectivity towards C2H6(even with a lower space velocity relative to without H2). These results demonstrate the ability of heteroatom composition to tune catalysis by using C2H4dimerization catalysis as a test reaction with zeolite Beta supported Ni catalysts.
- Meloni, Michael,Runnebaum, Ron C.
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p. 3393 - 3401
(2021/06/06)
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- Trioxatriangulenium (TOTA+) as a robust carbon-based Lewis acid in frustrated Lewis pair chemistry
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We report the reactivity between the water stable Lewis acidic trioxatriangulenium ion (TOTA+) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid-base interaction was analyzedviavariable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe3, led to the formation of a Lewis acid-base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P(tBu)3. The TOTA+-P(tBu)3FLP was characterized as an encounter complex, and found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of the C-Br bonds, and interception of Staudinger reaction intermediates. Moreover, TOTA+and NHC were found to first undergo single-electron transfer (SET) to form [TOTA]·[NHC]˙+, which was confirmedviaelectron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA-NHC]+adduct or a mixture of products depending the reaction conditions used.
- Shaikh, Aslam C.,Veleta, José M.,Moutet, Jules,Gianetti, Thomas L.
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p. 4841 - 4849
(2021/04/14)
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- Oxidative Addition of Aryl and Alkyl Halides to a Reduced Iron Pincer Complex
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The two-electron oxidative addition of aryl and alkyl halides to a reduced iron dinitrogen complex with a strong-field tridentate pincer ligand has been demonstrated. Addition of iodobenzene or bromobenzene to (3,5-Me2MesCNC)Fe(N2)2 (3,5-Me2MesCNC = 2,6-(2,4,6-Me-C6H2-imidazol-2-ylidene)2-3,5-Me2-pyridine) resulted in rapid oxidative addition and formation of the diamagnetic, octahedral Fe(II) products (3,5-Me2MesCNC)Fe(Ph)(N2)(X), where X = I or Br. Competition experiments established the relative rate of oxidative addition of aryl halides as I > Br > Cl. A linear free energy of relative reaction rates of electronically differentiated aryl bromides (ρ = 1.5) was consistent with a concerted-type pathway. The oxidative addition of alkyl halides such as methyl-, isobutyl-, or neopentyl halides was also rapid at room temperature, but substrates with more accessible β-hydrogen positions (e.g., 1-bromobutane) underwent subsequent β-hydride elimination. Cyclization of an alkyl halide containing a radical clock and epimerization of neohexyl iodide-d2 upon oxidative addition to (3,5-Me2MesCNC)Fe(N2)2 are consistent with radical intermediates during C(sp3)-X bond cleavage. Importantly, while C(sp2)-X and C(sp3)-X oxidative addition produces net two-electron chemistry, the preferred pathway for obtaining the products is concerted and stepwise, respectively.
- Rummelt, Stephan M.,Peterson, Paul O.,Zhong, Hongyu,Chirik, Paul J.
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p. 5928 - 5936
(2021/05/06)
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- Multiple N-H and C-H Hydrogen Atom Abstractions through Coordination-Induced Bond Weakening at Fe-Amine Complexes
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We report the use of the reported Fe-phthalocyanine complex, PcFe (1; Pc = 1,4,8,11,15,18,22,25-octaethoxy-phthalocyanine), to generate PcFe-amine complexes 1-(NH3)2, 1-(MeNH2)2, and 1-(Me2NH)2. Treatment of 1 or 1-(NH3)2 to an excess of the stable aryloxide radical, 2,4,6-tritert-butylphenoxyl radical (tBuArO?), under NH3 resulted in catalytic H atom abstraction (HAA) and C-N coupling to generate the product 4-amino-2,4,6-tritert-butylcyclohexa-2,5-dien-1-one (2) and tBuArOH. Exposing 1-(NH3)2 to an excess of the trityl (CPh3) variant, 2,6-di-tert-butyl-4-tritylphenoxyl radical (TrArO?), under NH3 did not lead to catalytic ammonia oxidation as previously reported in a related Ru-porphyrin complex. However, pronounced coordination-induced bond weakening of both α N-H and β C-H in the alkylamine congeners, 1-(MeNH2)2 and 1-(Me2NH)2, led to multiple HAA events yielding the unsaturated cyanide complex, 1-(MeNH2)(CN), and imine complex, 1-(MeN═CH2)2, respectively. Subsequent C-N bond formation was also observed in the latter upon addition of a coordinating ligand. Detailed computational studies support an alternating mechanism involving sequential N-H and C-H HAA to generate these unsaturated products.
- Wang, Zongheng,Johnson, Samantha I.,Wu, Guang,Ménard, Gabriel
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supporting information
p. 8242 - 8251
(2021/06/25)
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- RED SLUDGE USED AS A CATALYST FOR OLEFIN ISOMERIZATION
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The invention relates to systems and a method for isomerizing a charge to form a stream of alpha-olefin product. An example of a process includes calcination of red mud, flow of an olefin feedstock onto red sludge in an isomerization reactor, and separation of alpha-olefin from reactor effluent.
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Paragraph 0035
(2021/12/31)
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- Iridium-Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis
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Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium-catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4-chlorobutan-2-one or tert-butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional-group tolerance and safety profile of these reactions compared to the state-of-the-art. This method has granted access to alkenyl halide compounds containing acid-sensitive groups, such as tertiary alcohols, silyl ethers, and acetals. The synthetic value of those methodologies has been demonstrated by gram-scale synthesis where low catalyst loading was achieved.
- Yu, Peng,Bismuto, Alessandro,Morandi, Bill
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supporting information
p. 2904 - 2910
(2020/01/25)
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- Acid Properties of Cesium-Nickel-Zirconium Complex Phosphates: Effect on Isobutanol Dehydration
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Abstract: The physicochemical and catalytic properties of Cs1 – 2xNixZr2(PO4)3 (x = 0, 0.15, 0.25, 0.50) systems are studied. Double and triple nickel-containing phosphates with the NASICON structure are obtained by the sol–gel method. It is shown that these phosphates are active and stable isobutanol dehydration catalysts. The relationship between the catalytic activity in the dehydration reaction over triple cesium-zirconium phosphates and their crystallographic characteristics and surface acidity is established. It is shown that upon partial or complete replacement of cesium ions with nickel ions an increase in dehydration activity correlates with an increase in the number of acid sites determined by the pyridine adsorption titration method.
- Akhmedova, L. S.,Fionov, Yu. A.,Knyazeva, E. I.,Pylinina, A. I.,Sokolova, E. A.
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p. 592 - 596
(2020/05/29)
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- NASICON Catalysts with Composition Na(Cs)1 – 2xMxZr2(PO4)3 for Transformations of Aliphatic Alcohols
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Abstract: The activity of solid electrolytes from the family of Na(Cs)–Mx–Zr phosphates (NZP and CZP) with dopant ions M+2 = Co+2 and Ni+2 synthesized by the sol–gel method is studied in the gas-phase transformations of isopropanol and isobutanol. It is found that the amount of M+2 and its nature, as well as the direction of a change in the catalyst temperature (heating or cooling in the range of 473?693 K), affects the activity of M-NZP and M-CZP. In the transformation of isopropanol, hysteresis of the acetone yield, counter-clockwise (type I) for Co-NZP and clockwise (type II) for Ni-NZP, is observed in the heating–cooling cycles. An increase in the activity of Co-NZP in the cooling mode (type I) is related to a rise in the apparent activation energy of alcohol dehydrogenation under conditions of the formation of new catalytically active sites in the form of a Co+2?Zr+4 → Co+3?Zr+3 ion pair with the oxidized form of M and the reduced form of Zr. Type I hysteresis of the total alcohol conversion is observed in the transformations of isobutanol to olefin and aldehyde over Co(Ni)-CZP. The hysteresis is associated with a decrease in the activation energy of alcohol dehydrogenation. The main reaction over the Co(Ni)-CZP catalysts is the dehydration of alcohol with an increase in the activation energy of the reaction upon cooling, for example, by 53 kJ/mol for Ni0.25-CZP.
- Knyazeva, E. I.,Mikhalenko, I. I.,Pylinina, A. I.
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p. 1176 - 1183
(2020/10/14)
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- METHOD FOR PRODUCING ISOBUTYLENE
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PROBLEM TO BE SOLVED: To provide a method with relevant conventional technology as the background, for making it possible to produce isobutylene from isobutane at a relatively low temperature with a low-temperature high-activity dehydrogenation catalyst under economically advantageous conditions. SOLUTION: A method for producing isobutylene through direct dehydrogenation of isobutane includes the step of allowing a gas material containing isobutane to circulate in a catalyst layer filled with a dehydrogenation catalyst containing zeolite with platinum and iron supported thereon. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0043-0076
(2020/12/09)
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- Tuning Catalytic Sites on Zr6O8 Metal-Organic Framework Nodes via Ligand and Defect Chemistry Probed with tert-Butyl Alcohol Dehydration to Isobutylene
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Metal-organic frameworks (MOFs) have drawn wide attention as candidate catalysts, but some essential questions about their nature and performance have barely been addressed. (1) How do OH groups on MOF nodes act as catalytic sites (2) What are the relationships among these groups, node defects, and MOF stability, and how do reaction conditions influence them (3) What are the interplays between catalytic properties and transport limitations To address these questions, we report an experimental and theoretical investigation of the catalytic dehydration of tert-butyl alcohol (TBA) used to probe the activities of OH groups of Zr6O8 nodes in the MOFs UiO-66 and MOF-808, which have different densities of vacancy sites and different pore sizes. The results show that (1) terminal node OH groups are formed as formate and/or acetate ligands present initially on the nodes react with TBA to form esters, (2) these OH groups act as catalytic sites for TBA dehydration to isobutylene, and (3) TBA also reacts to break node-linker bonds to form esters and thereby unzip the MOFs. The small pores of UiO-66 limit the access of TBA and the reaction with the formate/acetate ligands bound within the pores, whereas the larger pores of MOF-808 facilitate transport and favor reaction in the MOF interior. However, after removal of the formate and acetate ligands by reaction with methanol to form esters, interior active sites in UiO-66 become accessible for the reaction of TBA, with the activity depending on the density of defect sites with terminal OH groups. The number of vacancies on the nodes is important in determining a tradeoff between the catalytic activity of a MOF and its resistance to unzipping. Computations at the level of density functional theory show how the terminal OH groups on node vacancies act as Br?nsted bases, facilitating TBA dehydration via a carbocation intermediate in an E1 mechanism; the calculations further illuminate the comparable chemistry of the unzipping.
- Babucci, Melike,Gaggioli, Carlo Alberto,Gagliardi, Laura,Gates, Bruce C.,Ray, Debmalya,Yang, Dong
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p. 8044 - 8056
(2020/04/30)
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- Reductive activation of PdII-precatalysts: Via decarboxylation of pivalate in direct C-H arylation reactions
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The mechanism of the reductive activation of PdII pre-catalysts has been extensively studied, but remains poorly understood. Herein, a combined computational and experimental approach is employed to clearly identify a PdII reduction process that has not been considered thus far. Pivalate, assumed to be a general base, was found to decarboxylate and act as a reductant, suggesting an alternative explanation for the superior performance of pivalic acid as an additive in Pd-catalyzed direct C-H arylation reactions.
- Kim, Seoung-Tae,Baik, Mu-Hyun
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supporting information
p. 13868 - 13871
(2020/11/18)
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- Phosphonate-Modified UiO-66 Br?nsted Acid Catalyst and Its Use in Dehydra-Decyclization of 2-Methyltetrahydrofuran to Pentadienes
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Phosphorus-modified all-silica zeolites exhibit activity and selectivity in certain Br?nsted acid catalyzed reactions for biomass conversion. In an effort to achieve similar performance with catalysts having well-defined sites, we report the incorporation of Br?nsted acidity to metal–organic frameworks with the UiO-66 topology, achieved by attaching phosphonic acid to the 1,4-benzenedicarboxylate ligand and using it to form UiO-66-PO3H2 by post-synthesis modification. Characterization reveals that UiO-66-PO3H2 retains stability similar to UiO-66, and exhibits weak Br?nsted acidity, as demonstrated by titrations, alcohol dehydration, and dehydra-decyclization of 2-methyltetrahydrofuran (2-MTHF). For the later reaction, the reported catalyst exhibits site-time yields and selectivity approaching that of phosphoric acid on all-silica zeolites. Using solid-state NMR and deprotonation energy calculations, the chemical environments of P and the corresponding acidities are determined.
- Caratzoulas, Stavros,Chen, Tso-Hsuan,Dauenhauer, Paul,Dorneles de Mello, Matheus,Han, Songi-I,Jain, Sheetal K.,Kumar, Gaurav,Li, Xinyu,Scott, Susannah L.,Tabassum, Tarnuma,Tsapatsis, Michael,Vlachos, Dionisios G.
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supporting information
p. 13260 - 13266
(2020/06/08)
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- Deoxygenation of Epoxides with Carbon Monoxide
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The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO2 from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C?O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration.
- Maulbetsch, Theo,Jürgens, Eva,Kunz, Doris
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p. 10634 - 10640
(2020/07/30)
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- CATALYST SYSTEMS THAT INCLUDE METAL OXIDE CO-CATALYSTS FOR THE PRODUCTION OF PROPYLENE
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Embodiments of methods of synthesizing a metathesis catalyst system, which include impregnating tungsten oxide on silica support in the presence of a precursor to produce a base catalyst; calcining the base catalyst; impregnating a metal oxide co-catalyst comprising a metal oxide onto the surface of the base catalyst to produce a doped catalyst; and calcining the doped catalyst to produce a metathesis catalyst system. Further embodiments of processes for the production of propylene, which include contacting a hydrocarbon feedstock comprising a mixture of 1-butene and 2-butene with embodiments of the metathesis catalyst system to produce, via metathesis conversion, a product stream comprising propylene.
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Paragraph 0069-0070
(2020/05/02)
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- Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction
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A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.
- Banert, Klaus,Hagedorn, Manfred,Heck, Manuel,Hertel, Raphael,Ihle, Andreas,Müller, Ioana,Pester, Tom,Shoker, Tharallah,Rablen, Paul R.
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p. 13630 - 13643
(2020/11/13)
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- PROCESS AND CATALYSTS FOR THE PRODUCTION OF DIESEL AND GASOLINE ADDITIVES FROM GLYCEROL
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A method of producing one or more glycerol ethers, the method comprising contacting glycerol and tertiary butanol (TBA) in the presence of an acidic catalyst to produce one or more glycerol ethers selected from mono-tert butyl glycerol ethers, di-tert butyl glycerol ethers, tri-tert butyl glycerol ethers, or a combination thereof; separating water and a stream comprising isobutylene, unreacted TBA, or a combination thereof from the one or more glycerol ethers; and recycling at least a portion of the stream comprising isobutylene, unreacted TBA, or a combination thereof to the contacting. Also disclosed is a process of co-producing isooctene, wherein the process involves contacting glycerol and tertiary butanol in the presence of a dehydrating catalyst and dimerizing/oligomerizing the dehydrated products in the presence of an oligomerizing catalyst to form isooctene, a precursor of isooctane and isomers thereof.
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Paragraph 0043-0045
(2020/01/24)
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- Photooxidation Reactions of Ethyl 2-Methylpropionate (E2MP) and Ethyl 2,2-Dimethylpropionate (E22DMP) Initiated by OH Radicals: An Experimental and Computational Study
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The relative rate (RR) technique was used for the measurement of OH-initiated photooxidation reactions of ethyl 2-methylpropionate (E2MP) and ethyl 2,2-dimethylpropionate (E22DMP) in the temperature range of 268-363 K at 760 Torr. In addition to this, the
- Kaipara, Revathy,Rajakumar, B.
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p. 2768 - 2784
(2020/05/08)
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- Sn-Catalyzed Criegee-Type Rearrangement of Peroxyoxindoles Enabled by Catalytic Dual Activation of Esters and Peroxides
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We report here the Sn-catalyzed mild protocol for ring expansion of peroxyoxindoles to afford the series of substituted-2H-benzo[b][1,4]oxazin-3(4H)-one derivatives. In this protocol, we showed the in situ conversion of tert-butyl peroxy compounds into peresters with the aid of external esters, which then underwent the ring-expansion process, and the incipient carbocation was trapped with the alcohol residue generated from the esters. The reaction is also demonstrated in a continuous flow process to afford the rearranged product in 22 min of residence time.
- Chaudhari, Moreshwar B.,Gnanaprakasam, Boopathy,Jayan, Krishna
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supporting information
p. 3374 - 3382
(2020/03/23)
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- O-(tert-butyl) Se-phenyl selenocarbonate: A convenient, bench-stable and metal-free precursor of benzeneselenol
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A study by our laboratory shows that air, light and moisture stable O-(tert-butyl) Se-phenyl selenocarbonate could be employed as a safer, practical and efficient alternative to generate “in situ” benzeneselenol or benzeneselenolate anion under different and transition metal-free conditions. This procedure seems to be of general application since the nucleophilic selenium species obtained can be trapped by electrophiles such as alkyl halides, epoxides and electron-deficient alkenes and alkynes under different reaction conditions.
- Temperini, Andrea,Siciliano, Carlo
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- Rotation-Triggered Transmetalation on a Heterobimetallic Cu/Al N-Phosphine-Oxide-Substituted Imidazolylidene Complex
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A novel strategy for the preparation of heterobimetallic N-heterocyclic carbene (NHC) complexes is demonstrated using N-phosphine-oxide-substituted imidazolylidenes (PoxIms). In these heterobimetallic Cu/Al complexes, the Cu and Al centers can be either completely separated or brought near each other via the rotation of the N-phosphinoyl group in the PoxIm ligands. Triggered by this rotation, transmetalation to exchange the Cu-OtBu and Al-C6F5 bonds occurs on in situ-generated Cu/Al PoxIm complexes, and the Cu-C6F5 and Al-OtBu bonds are formed in excellent yield. On the basis of the results of mechanistic studies, including the isolation/in situ observation of key complexes and theoretical calculations, a plausible reaction mechanism for an intramolecular transmetalation is proposed to proceed via an activation complex that includes the simultaneous coordination of the phosphinoyl oxygen atom to the Cu as well as the Al centers. Furthermore, the formation of carbon-carbon bonds between Al(C6F5)3 and allyl bromide mediated/catalyzed by Cu/Al PoxIm complexes is demonstrated. Upon the consecutive transfer of three C6F5 groups from a single molecule of Al(C6F5)3, allyl pentafluorobenzene derivatives were obtained. The present results demonstrate the role of phosphine oxide in the activation of organoaluminum reagents for the transmetalation between Cu(I) complexes bearing NHCs as well as the benefit of constructing an intramolecular system based on a heterobimetallic complex to achieve efficient transmetalation by programming the encounter of two organometallic fragments.
- Asada, Takahiro,Hoshimoto, Yoichi,Ogoshi, Sensuke
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supporting information
p. 9772 - 9784
(2020/07/10)
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- A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite
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There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.
- Chen, Wei,Corma, Avelino,De Baerdemaeker, Trees,De Vos, Dirk E.,Dong, Zhuoya,Kolb, Ute,Lei, Chi,Müller, Ulrich,Ma, Yanhang,Marler, Bernd,Martínez, Cristina,Martínez-Triguero, Joaquín,Meng, Xiangju,Parvulescu, Andrei-Nicolae,Wu, Qinming,Xiao, Feng-Shou,Yokoi, Toshiyuki,Zhang, Weiping,Zheng, Anmin
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supporting information
p. 15649 - 15655
(2020/07/04)
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- Synthesis and catalytic performance of zeolite-Y supported on silicon carbide in n-heptane cracking
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In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ～400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrostatically attracts negatively charged aluminosilicate seeds and promotes the growth of zeolite (ZY) particles over SiC, thus leading to the formation of stable ZY?SiC supported catalysts. The supported ZY catalysts with different weight ratio of ZY and SiC were synthesized and characterized by various techniques such as XRD, SEM, SEM-EDX, SEM-mapping, TEM, STEM, FT-IR, 27Al MAS NMR and N2 sorption. The characterization of the supported ZY catalysts suggests the uniform growth of ZY particles over SiC together with the creation of hierarchical micro-mesopores assembly. In the catalytic cracking of n-heptane, the catalyst ZY?SiC-50 displayed a remarkable improvement in reaction rate when compared to commercial zeolite-Y (CBV-600) amounting to 3.5 folds enhancement. Interestingly, the light olefins yield is also substantially improved. At WHSV of 8 h?1 and 475 °C, the highest light olefin yield (24–36 %) was achieved over ZY?SiC-50 whereas the reference catalyst, CBV-600 produced lower light olefins yield (7–17 %). Moreover, the supported ZY catalyst exhibited less deactivation rates. This improved performance is attributed to the hierarchical micro-mesopores assembly created by the homogeneous dispersion of zeolite crystals on SiC which offers fast diffusion pathways for the reactants and enhanced accessibility to active sites thus leading to higher observed reaction rates and fast diffusion of products thus minimizing the occurrence of side reactions.
- Alhassan, Saeed M.,Berthod, Mikael,Dabbawala, Aasif A.,Joseph, Tony,Khan, Shaihroz,Mittal, Hemant,Morin, Stephane,Singaravel, Gnana,Vaithilingam, Balasubramanian V.,Wahedi, Yasser Al
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- Primary Sulfonamide Synthesis Using the Sulfinylamine Reagent N-Sulfinyl- O-(tert-butyl)hydroxylamine, t-BuONSO
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Sulfonamides have played a defining role in the history of drug development and continue to be prevalent today. In particular, primary sulfonamides are common in marketed drugs. Here we describe the direct synthesis of these valuable compounds from organometallic reagents and a novel sulfinylamine reagent, t-BuONSO. A variety of (hetero)aryl and alkyl Grignard and organolithium reagents perform well in the reaction, providing primary sulfonamides in good to excellent yields in a convenient one-step process.
- Davies, Thomas Q.,Hall, Adrian,Skolc, David,Tilby, Michael J.,Willis, Michael C.
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supporting information
p. 9495 - 9499
(2020/12/21)
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- Wet and dry processes for the selective transformation of phosphonates to phosphonic acids catalyzed by br?nsted acids
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A "wet"process and two "dry"processes for converting phosphonate esters to phosphonic acids catalyzed by a Bronsted acid have been developed. Thus, in the presence of water, a range of alkyl-, alkenyl-, and aryl-substituted phosphonates can be generally hydrolyzed to the corresponding phosphonic acids in good yields catalyzed by trifluoromethyl sulfonic acid (TfOH) at 140 °C (the wet process). On the other hand, with specific substituents of the phosphonate esters, the conversion to the corresponding phosphonic acids can be achieved under milder conditions in the absence of water (the dry process). Thus, the conversion of dibenzyl phosphonates to the corresponding phosphonic acids took place smoothly at 80 °C in toluene or benzene in high yields. Moreover, selective conversion of benzyl phosphonates RP(O)(OR′)(OBn) to the corresponding mono phosphonic acids RP(O)(OR′)(OH) can also be achieved under the reaction conditions. The dealkylation via the generation of isobutene of ditert- butyl phosphonate, and the related catalysis by TfOH took place even at room temperature to give the corresponding phosphonic acids in good to high yields. Nafion also shows high catalytic activity for these reactions. By using Nafion as the catalyst, phosphonic acids could be easily prepared on a large scale via a simple process.
- Li, Chunya,Saga, Yuta,Onozawa, Shun-Ya,Kobayashi, Shu,Sato, Kazuhiko,Fukaya, Norihisa,Han, Li-Biao
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supporting information
p. 14411 - 14419
(2020/12/29)
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- Hydrogenative metathesis of enynes via piano-stool ruthenium carbene complexes formed by alkyne gem-hydrogenation
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The only recently discovered gem-hydrogenation of internal alkynes is a fundamentally new transformation, in which both H atoms of dihydrogen are transferred to the same C atom of a triple bond while the other position transforms into a discrete metal carbene complex. [Cp?RuCl]4 is presently the catalyst of choice: the resulting piano-stool ruthenium carbenes can engage a tethered alkene into either cyclopropanation or metathesis, and a prototypical example of such a reactive intermediate with an olefin ligated to the ruthenium center has been isolated and characterized by X-ray diffraction. It is the substitution pattern of the olefin that determines whether metathesis or cyclopropanation takes place: a systematic survey using alkenes of largely different character in combination with a computational study of the mechanism at the local coupled cluster level of theory allowed the preparative results to be sorted and an intuitive model with predictive power to be proposed. This model links the course of the reaction to the polarization of the double bond as well as to the stability of the secondary carbene complex formed, if metathesis were to take place. The first application of "hydrogenative metathesis"to the total synthesis of sinularones E and F concurred with this interpretation and allowed the proposed structure of these marine natural products to be confirmed. During this synthesis, it was found that gem-hydrogenation also provides opportunities for C-H functionalization. Moreover, silylated alkynes are shown to participate well in hydrogenative metathesis, which opens a new entry into valuable allylsilane building blocks. Crystallographic evidence suggests that the polarized [Ru-Cl] bond of the catalyst interacts with the neighboring R3Si group. Since attractive interligand Cl/R3Si contacts had already previously been invoked to explain the outcome of various ruthenium-catalyzed reactions, including trans-hydrosilylation, the experimental confirmation provided herein has implications beyond the present case.
- Peil, Sebastian,Bistoni, Giovanni,Goddard, Richard,Fürstner, Alois
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supporting information
p. 18541 - 18553
(2020/11/17)
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- Impact of Zeolite Framework Composition and Flexibility on Methanol-To-Olefins Selectivity: Confinement or Diffusion?
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The methanol-to-olefins reaction catalyzed by small-pore cage-based acid zeolites and zeotypes produces a mixture of short chain olefins, whose selectivity to ethene, propene and butene varies with the cavity architecture and with the framework composition. The product distribution of aluminosilicates and silicoaluminophosphates with the CHA and AEI structures (H-SSZ-13, H-SAPO-34, H-SSZ-39 and H-SAPO-18) has been experimentally determined, and the impact of acidity and framework flexibility on the stability of the key cationic intermediates involved in the mechanism and on the diffusion of the olefin products through the 8r windows of the catalysts has been evaluated by means of periodic DFT calculations and ab initio molecular dynamics simulations. The preferential stabilization by confinement of fully methylated hydrocarbon pool intermediates favoring the paring pathway is the main factor controlling the final olefin product distribution.
- Boronat, Mercedes,Corma, Avelino,Ferri, Pau,Li, Chengeng,Martínez-Triguero, Joaquín,Millán, Reisel,Moliner, Manuel
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supporting information
p. 19708 - 19715
(2020/08/21)
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- Synthesis and Catalytic Performance of a Dual-Sites Fe–Zn Catalyst Based on Ordered Mesoporous Al2O3 for Isobutane Dehydrogenation
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Abstract: Ordered mesoporous Zn/OMA-Fe materials were easily prepared via one pot evaporation induced self-assembly (EISA) method in combination with incipient wetness strategy. Dehydrogenation of isobutane to isobutene were carried out on these materials, the isobutane conversion of 50.7% and the yield of 37.8% were obtained over 13Zn/OMA-10Fe catalyst at 580?°C with 300?h?1 GHSV. The synthesized materials with large specific surface areas and uniform pore sizes were characterized by XRD, N2 adsorption–desorption, TEM, XPS, H2-TPR, M?ssbauer and NH3-TPD. A portion of Fe species were highly dispersed on the support surface and others incorporated into Al2O3 frameworks, Zn species existed in the form of hexagonal ZnO phase. The total acidity of these catalysts was increased by the introduction of Zn, facilitating the conversion of isobutane. Moreover, the conversion of Fe species might play a major role in improving isobutene selectivity. Graphical Abstract: [Figure not available: see fulltext.].
- Cheng, Ming,Zhao, Huahua,Yang, Jian,Zhao, Jun,Yan, Liang,Song, Huanling,Chou, Lingjun
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p. 1326 - 1336
(2019/03/02)
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- Facile synthesis of ordered mesoporous zinc alumina catalysts and their dehydrogenation behavior
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Ordered mesoporous Zn/Al2O3 materials with varying Zn content were simply prepared via an evaporation-induced self-assembly (EISA) method. Dehydrogenation of isobutane to isobutene was carried out on these materials; an isobutane conversion of 45.0% and isobutene yield of 39.0% were obtained over the 10%Zn/Al2O3 catalyst at 580?°C with 300 h?1 GHSV. The obtained materials with Zn content up to 10% possess large specific surface area and big pore volume and zinc species can be highly dispersed on the surface or incorporated into the framework. The acidity of these catalysts was changed by the introduction of Zn, the decrease of strong acid sites is conducive to the promotion of isobutene selectivity and the weak and medium acidic sites played an important role in isobutane conversion. In addition, these catalysts exhibited good catalytic stability, due to the effective inhibition of coke formation by the ordered mesoporous structure.
- Cheng, Ming,Zhao, Huahua,Yang, Jian,Zhao, Jun,Yan, Liang,Song, Huanling,Chou, Lingjun
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p. 9828 - 9837
(2019/04/01)
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- SULFUR INJECTION IN FLUIDIZATION BED DEHYDROGENATION ON CHROMIUM CATALYST FOR DEHYDROGENATION PROCESS IMPROVEMENT AND PROCESS SCHEME OPTIMIZATION
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Systems and processes for producing isomerized alkenes are disclosed. The systems mainly include an isomerization unit, a dehydrogenation unit, and a MTBE synthesis unit. A hydrocarbon stream is fed into the isomerization unit to form iso-alkanes in a sulfur free hydrocarbon stream. The sulfur free hydrocarbon stream is heated and then combined with a sulfur-containing hydrocarbon stream comprising sulfur containing compounds to form a reactant feed stream to the dehydrogenation unit. The iso- alkanes is dehydrogenated to form iso-alkenes. The formed iso- alkenes comprising isobutylene can be used as a feed stock for the MTBE synthesis unit.
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Paragraph 0025-0030; 0055-0059
(2019/07/13)
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- Targeted Synthesis of a Zeolite with Pre-established Framework Topology
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Given their great potential as new industrial catalysts and adsorbents, the search for new zeolite structures is of major importance in nanoporous materials chemistry. However, although innumerable theoretical frameworks have been proposed, none of them have been synthesized by a priori design yet. We generated a library of diazolium-based cations inspired from the organic structure-directing agents (OSDAs) recently reported to give two structurally related zeolites (PST-21 and PST-22) under highly concentrated, excess-fluoride conditions and compared the stabilization energies of each OSDA cation in ten pre-established hypothetical structures. A combination of the ability of the OSDA selected in this way with the excess-fluoride approach has allowed us to crystallize PST-30, the targeted aluminosilicate zeolite structure. We anticipate that our approach, which aims to rationally couple computational predictions of OSDAs with an experimental setup, will advance further development in the synthesis of zeolites with desired properties.
- Jo, Donghui,Hong, Suk Bong
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supporting information
p. 13845 - 13848
(2019/08/26)
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- METHOD OF PRODUCING ISOBUTENE
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PROBLEM TO BE SOLVED: To provide a production method enabling activity of γ-alumina catalyst to be maintained and enabling isobutene to be obtained from tert-butyl alcohol at high yield. SOLUTION: The method of producing isobutene is provided that includes a step of contacting tert-butyl alcohol with a γ-alumina catalyst having an Na content of less than 0.1 mass% in terms of Na2O. In the method of producing isobutene, it is preferable that Si content of the γ-alumina catalyst in terms of SiO2 is less than 0.5 mass%. It is also preferable that specific surface area of the γ-alumina catalyst is 100 to 300 m2/g. Further it is preferable that the tert-butyl alcohol and the γ-alumina catalyst are contacted with each other at a temperature in the range of 180 to 370°C. SELECTED DRAWING: None COPYRIGHT: (C)2020,JPOandINPIT
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Paragraph 0020-0026
(2019/12/03)
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- Thermal analysis of salts from 4-nitrophenol and aliphatic amines
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Solid samples obtained from 4-nitrophenol and aliphatic amines, in excess of amine, were submitted to thermal analysis. The TGA/DTA showed two endothermic events, with exception of tert-butylamine, which showed three endothermic peaks. The first event was the melting of the ionic salt, which temperature does not follow a pattern, and is maxim for ethylammonium minimal for butylammonium salt. For methylammonium and ethylammonium, the fusion is followed by mass loss corresponding to one amine by 4-nitrophenol, while for the others ammonium salts, this event marks the beginning of the mass variation, that is maintained until the decomposition of the 4-nitrophenol at 485?K. The temperature of the event depends of the length of the chain of the amine, while the second occurs at the same temperature for all amines.
- Lazzarotto, Márcio,Nachtigall, Francine Furtado,de Siqueira, Geisa Liandra de Andrade,da Silveira Lazzarotto, Simone Rosa,Lazzarotto, Marcelo
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p. 351 - 357
(2019/04/17)
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- Synthesis of β-ketoiminate and β-iminoesterate tungsten (VI) oxo-alkoxide complexes as AACVD precursors for growth of WOx thin films
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The tungsten (VI) oxo-alkoxide complexes WO(OR)3L [R = tBu; L = acNac, etNac, tbNac, acNacMe, acNacEt] (1–5) and WO(OCH3)3(acNac) (6) have been synthesized. The isomeric purity of these complexes depends on the steric bulk of the substituent on the imino nitrogen of the chelating ligand. The thermal properties of the complexes have been evaluated to assess the effect of the β-ketoiminate or β-iminoesterate ligands. WO(OC(CH3)3)3(acNac) (1) has been used as a precursor for aerosol assisted chemical vapor deposition (AACVD) of WOx thin films at temperatures from 250 to 450 °C. The results of mass spectrometry and thermolysis studies have been used to propose possible precursor decomposition pathways during film deposition.
- Su, Xiaoming,Kim, Taehoon,Abboud, Khalil A.,McElwee-White, Lisa
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p. 548 - 557
(2018/11/10)
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- Visualizing Formation of Intermetallic PdZn in a Palladium/Zinc Oxide Catalyst: Interfacial Fertilization by PdHx
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Controllable synthesis of well-defined supported intermetallic catalysts is desirable because of their unique properties in physical chemistry. To accurately pinpoint the evolution of such materials at an atomic-scale, especially clarification of the initial state under a particular chemical environment, will facilitate rational design and optimal synthesis of such catalysts. The dynamic formation of a ZnO-supported PdZn catalyst is presented, whereby detailed analyses of in situ transmission electron microscopy, electron energy-loss spectroscopy, and in situ X-ray diffraction are combined to form a nanoscale understanding of PdZn phase transitions under realistic catalytic conditions. Remarkably, introduction of atoms (H and Zn in sequence) into the Pd matrix was initially observed. The resultant PdHx is an intermediate phase in the intermetallic formation process. The evolution of PdHx in the PdZn catalyst initializes at the PdHx/ZnO interfaces, and proceeds along the PdHx ?111? direction.
- Niu, Yiming,Liu, Xi,Wang, Yongzhao,Zhou, Song,Lv, Zhengang,Zhang, Liyun,Shi, Wen,Li, Yongwang,Zhang, Wei,Su, Dang Sheng,Zhang, Bingsen
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supporting information
p. 4232 - 4237
(2019/02/16)
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- METHOD FOR PRODUCING CONJUGATED DIENE
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Provided is a method of producing a conjugated diene, including a step of dehydrating a γ,δ-unsaturated alcohol in the presence of a solid acid catalyst having a Hammett acidity function (H0) of ?12.2 or less.
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Paragraph 0058-0059
(2019/05/18)
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- Chemical Vapor Deposition of Phase-Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors
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Homoleptic uranium(IV) amidate complexes have been synthesized and applied as single-source molecular precursors for the chemical vapor deposition of UO2 thin films. These precursors decompose by alkene elimination to give highly crystalline ph
- Straub, Mark D.,Leduc, Jennifer,Frank, Michael,Raauf, Aida,Lohrey, Trevor D.,Minasian, Stefan G.,Mathur, Sanjay,Arnold, John
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p. 5749 - 5753
(2019/04/16)
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